Survey of Ion Properties in Jupiter's Plasma Sheet: Juno JADE‐I Observations

Kim, Thomas K.; Ebert, R. W.; Valek, P. W.; Allegrini, F.; McComas, D. J.; Bagenal, F.; Connerney, J. E. P.; Livadiotis, G.; Thomsen, M. F.; Wilson, R. J.; Bolton, S. J.

doi:10.1029/2019ja027696

Cited by 52 publications

(137 citation statements)

References 65 publications

(154 reference statements)

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“…The distribution of H + in Figure 8 has a minimum at 10 R J around the O + peak, since H + distributes there along the magnetic field lines at high latitudes (Figure 4). (Kim et al, 2020). The value displayed by orange triangles in Figure 8 as O + is the sum of O + , S + , S ++ and S +++ .…”

Section: Comparison With Observationsmentioning

confidence: 99%

Global Simulation of the Jovian Magnetosphere: Transitional Structure From the Io Plasma Disk to the Plasma Sheet

et al. 2021

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The structure and dynamics of the Jupiter's magnetosphere are very different from those of the earth. The planet's magnetic field is 14 times stronger than that of the earth. Such strong magnetic field and the dilute solar wind (Hanlon et al., 2004) result in the formation of a huge magnetosphere. In the Jovian magnetosphere, the average position of the bow shock is around 80 R J in front of the planet (Achilleos et al., 2004;Sarkango et al., 2019). The plasma sheet forms in the similar way as the Earth, but the plasma sheet mainly consists of plasma from the moon Io. The radius of Jupiter is 11 times larger than that of the Earth. The planetary rotation period is as short as 10 h. High-speed planetary rotation is also transmitted to Io plasma. The magnetic axis tilts about 10° from the rotation axis (Smyth et al., 2011). The shape of magnetic field deviates from the dipole, with an anomaly that provides a weak magnetic field region at high latitudes in the Northern Hemisphere (Hess et al., 2011).Io's orbit is at 5.95 R J , where neutral gas is released. Diffusing gas is ionized, then about half is picked up by rotating magnetic field. The amount of plasma supplied from Io is 0.26-1.4 t/sec (Delamere & Bagenal, 2003). The plasma components from Io are O + , O ++ , S + , S ++ , S +++ , and Na + (Bodish et al., 2017;Kim et al., 2020). This Io source plasma plays a major role in constructing the inner magnetosphere, in forming the magnetosphere-ionosphere (M-I) coupling system. Io plasma forms the plasma disk in the inner magnetosphere (<15 R J ), and the plasma sheet in the middle tail (20 R J ∼ 60 R J ). Io source plasma is predominant over these regions (Cohen et al., 2001;Radioti et al., 2005). In the distant tail (>600 R J ), plasma originating from the solar wind is predominant (McComas et al., 2017).In the inner magnetosphere, Io plasma accumulates and becomes unstable when the density exceeds a certain level (Southwood & Kivelson, 1987). Through the interchange instability possibly caused by the

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Section: Comparison With Observationsmentioning

confidence: 99%

Global Simulation of the Jovian Magnetosphere: Transitional Structure From the Io Plasma Disk to the Plasma Sheet

et al. 2021

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“…The next step is to test this simple functional form for the centrifugal equator against Juno observations of the thermal plasma in Jupiter's magnetosphere (Bagenal et al, 2017). Juno's JADE instrument (McComas et al, 2017) has been observing plasma properties primarily in the outer magnetosphere and over Jupiter's poles (e.g., Ebert et al, 2017;Kim et al, 2020;Szalay et al, 2017;Valek et al, 2019 the Juno gravity signals have been used to determine plasma properties in the Io plasma torus (R = 5-10 R J ) (Phipps et al, 2018(Phipps et al, , 2019. Phipps et al (2020) compared the geometry of the radio occultations (where the path of Juno's radio communication with Earth is modulated by the electron density as it passes through the Io plasma torus) to a modeled centrifugal equator and found similarities in longitude variability in torus densities.…”

Section: Future Workmentioning

confidence: 99%

Centrifugal Equator in Jupiter’s Plasma Sheet

Phipps

Bagenal

2021

JGR Space Physics

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In Jupiter’s magnetosphere, the structure of the plasma sheet depends on the magnetic field geometry and the centrifugal forces on the plasma. We present a simple formulation for the centrifugal equator, the farthest point along a magnetic flux tube from the planetary spin axis, for Jupiter’s torus to plasma sheet region (5–30 jovian radii). The formulation is based on a dipole magnetic field and azimuthally symmetric current sheet, both tilted by 9.5° toward System III west longitude of 201°. We find a good fit to such a model with a hyperbolic tangent function varying sinusoidally with longitude. The latitudinal angle of the derived centrifugal equator relative to the jovigraphic equator changes from the dipolar value (2/3 of the dipole tilt) around 5 jovian radii to close to the full dipole tilt at 25 jovian radii.

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“…We group all ions with M/q ≥ 7 as heavy ions. A detailed description of the TOF section and how secondary foil effects are used to extend the mass resolution is given in Kim et al (2019Kim et al ( , 2020. The trajectories-as viewed from the sunward direction-are nearly identical in latitude and altitude, differing primarily in longitude.…”

Section: Datamentioning

confidence: 99%

Juno In Situ Observations Above the Jovian Equatorial Ionosphere

Valek

Bagenal

Ebert

et al. 2020

Geophysical Research Letters

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The arrival of Juno at Jupiter enables repeated in situ observations above the Jovian ionosphere. The low altitude and high velocity of Juno at perijove permits direct sampling of ionospheric ion populations. We present the first direct observations above the ionosphere made by the Jovian Auroral Distributions Experiment Ion sensor (JADE-I). When looking into the spacecraft ram direction, JADE-I can measure ion energy distributions to below 1 eV/q along with ion composition. We report observations from 17 Juno perijove passes. At these latitudes, the low energy ions consist of protons and heavier ions, protons being the dominant species. Heavy ions-primarily oxygen and sulfur likely originating from the magnetosphere-are seen each pass, but their intensity varies. Other trace light ions are observed during some of the perijoves: H 3 + (6 of 17 perijoves), He + (2 of 17 perijoves). Ionospheric ions are observed up to altitudes of~7,000 km. Plain Language Summary The high speed of the Juno spacecraft permits its lower energy ion sensor-JADE-I-to chase down and observe low energy ions that have not been directly observed before. When looking into the direction the spacecraft is moving (i.e., the spacecraft ram direction), this sensor can observe ionospheric ions that are at a near-zero velocity in the rest frame of Jupiter. This permits direct observations of the ion population above Jupiter's ionosphere for the first time. Here, we present those observations for 17 close fly-bys at equatorial latitudes. We observe that the cold ion population contains a range of species. The dominant species is protons. Seen in each pass are also heavier oxygen and sulfur ions, but the intensity of these heavy ions varies from pass to pass. The presence of these heavy ions shows that there is some form of coupling between Jupiter and material on magnetic field lines far away from the planet, but the mechanism is not clear from these observations. Other light ions are also seen for some of the passes: H 3 + for six of 17 passes, He + for two of 17 passes.

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Survey of Ion Properties in Jupiter's Plasma Sheet: Juno JADE‐I Observations

Cited by 52 publications

References 65 publications

Global Simulation of the Jovian Magnetosphere: Transitional Structure From the Io Plasma Disk to the Plasma Sheet

Global Simulation of the Jovian Magnetosphere: Transitional Structure From the Io Plasma Disk to the Plasma Sheet

Centrifugal Equator in Jupiter’s Plasma Sheet

Juno In Situ Observations Above the Jovian Equatorial Ionosphere

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